FLAME SPREAD ON AVIATION FUELS

Flame spread rates and flame spread induction times have been measured for JP-5, JP-8 and mixtures of these fuels over the temperature range 10-90 degrees C. The flame spread data were correlated on the basis o f the initial liquid temperature relative to the closed cup flashpoint . Liquid-phase-controlled flame spread is observed for liquid temperat ures <15 degrees C above the closed cup flashpoint and the flame sprea d rate ranges from 3 to 12 cm/s depending on the liquid temperature re lative to the flashpoint. For liquid temperatures >15 degrees C above the closed cup flashpoint, flame spread is via gas-phase-controlled fl ame spread and flame spread rates range from 12 to 160 cm/s. The trans ition at V = 12 cm/s and the maximum flame spread rate are consistent with present knowledge of gas-phase flame spread and burning velocitie s. Differences between the present data and other available data from the literature are the result of differences in flashpoint interpretat ion for hydrocarbons versus alcohols and the use of very narrow flame spread pans by early investigators. The use of pans of only 1-6 cm cau ses large changes in flame spread rate with temperature which are not observed in wider pans. Therefore the use of narrow tray flame spread experiments gives an incorrect indication of the flame spread rate to be expected in large-scale (realistic) conditions. Pan widths of at le ast 20 cm are required to avoid these small-pan-width effects. Variati ons in the flashpoint of mixtures of JP fuels were successfully predic ted using the method of Affens and McLaren by treating each JP fuel as a single fuel characterized by a single vapour pressure-temperature r elation and assuming that mole fractions in the liquid phase may be ap proximated by the volume fraction of the JP fuel. Flame spread inducti on times were shown to be a function of the liquid temperature relativ e to the closed cup flashpoint. The induction time was also shown to b e dependent on the strength and nature of the ignition source. (C) 199 7 Elsevier Science Ltd.